Nothing to do with game optimisation, I'm afraid - Ren'py and Android just don't play well together sometimes, especially in the case of newer model phones running the latest OS. PyTom (the creator of Ren'py) is in a perpetual state of trying to catch up with the latest changes to Android.
That being said, is the game crashing randomly after a minute or is it always at a specific point?
If it's random then it'll be an incompatibility between your device, your Android OS and Ren'py, in which case the only solution is to download JoiPlay ( https://play.google.com/store/apps/details?id=cyou.joiplay.joiplay&hl=en_GB&gl=U... ) and install the WIN version of the game (it's identical to the Android version).
If it's always at a specific point then it will be an issue specifically with your phone or ISP - either drivers have gone wonky or haven't been updated correctly, there's not enough storage, the download was corrupted or else something super esoteric like you unplugged your headphones (which causes Ren'py to black screen sometimes, for no discernible reason).